High-power laser systems are utilized for a host of different applications, such as welding, cutting, drilling, and materials processing. Such laser systems typically include a laser emitter, the laser light from which is coupled into an optical fiber (or simply a “fiber”), and an optical system that focuses the laser light from the fiber onto the workpiece to be processed. Wavelength beam combining (WBC) is a technique for scaling the output power and brightness from laser diodes, laser diode bars, stacks of diode bars, or other lasers arranged in a one- or two-dimensional array. WBC methods have been developed to combine beams along one or both dimensions of an array of emitters. Typical WBC systems include a plurality of emitters, such as one or more diode bars, that are combined using a dispersive element to form a multi-wavelength beam. Each emitter in the WBC system individually resonates, and is stabilized through wavelength-specific feedback from a common partially reflecting output coupler that is filtered by the dispersive element along a beam-combining dimension. Exemplary WBC systems are detailed in U.S. Pat. No. 6,192,062, filed on Feb. 4, 2000, U.S. Pat. No. 6,208,679, filed on Sep. 8, 1998, U.S. Pat. No. 8,670,180, filed on Aug. 25, 2011, and U.S. Pat. No. 8,559,107, filed on Mar. 7, 2011, the entire disclosure of each of which is incorporated by reference herein.
While techniques such as WBC have succeeded in producing laser-based systems for a wide variety of applications, wider adoption of such systems has resulted in the demand for ever-higher levels of laser output power. Typically higher laser powers involve the driving of laser diodes at increasingly higher currents, which results in higher operating temperatures and concomitant thermal-management issues aimed at preventing temperature-based reliability issues. One such issue is solder creep. High-power lasers typically feature the use of a laser emitter with one or more heat sinks or other thermal-management structures for heat dissipation, and these structures are often coupled to the emitter via a solder or other soft, malleable compound that maintains thermal contact between the emitter and heat sink even in the event of relative movement between the components resulting from thermal cycling.
While such solder-based solutions mitigate some of the reliability issues resulting from thermal cycling during high-power laser operation, the use of solder may also introduce other reliability issues such as solder creep. During solder creep, the solder develops internal voids that can coalesce and lead to crack nucleation. In addition, the solder may slowly work its way out from between the two mating surfaces. This problem is exacerbated by the fact that the components between which the solder is placed are typically clamped or screwed together in order to squeeze the components together and minimize any thermal distortion. This clamping force may increase the solder-creep rate, particularly during high-temperature operation when the solder is typically softer and more flowable.
Thus, there is a need for improved thermal-management systems for high-power lasers (e.g., laser diodes), particularly such systems that also mitigate creep of solder or other flowable joining compounds.